EP2801452A2

EP2801452A2 - Articulated mechanical arm

Info

Publication number: EP2801452A2
Application number: EP14167150.3A
Authority: EP
Inventors: Young Bo Shim; Young Do Kwon; Byung June Choi; Yong Jae Kim; Kyung Shik Roh; Min Hyung Lee
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2013-05-07
Filing date: 2014-05-06
Publication date: 2014-11-12
Anticipated expiration: 2034-05-06
Also published as: KR20140132837A; US9416855B2; KR102127215B1; JP2014217943A; CN104141762A; US20140331798A1; CN104141762B; EP2801452B1; JP6408767B2; EP2801452A3

Abstract

The invention relates to an articulated mechanical arm. The mechanical arm comprises a link unit; and a drive unit configured to drive the link unit; wherein the link unit comprises: a first link; a second link rotatably coupled to the first link; a third link rotatably coupled to the second link; a plurality of wires, each of which is fixed at one end thereof to the third link, and is connected at the other end thereof to the drive unit, and through which a driving force is transmitted from the drive unit to the third link; a path forming structure configured to define for each of the wires a path between the drive unit and the third link; and a length holding structure configured to hold substantially constant a length that each of the wires extends between the drive unit and the third link.

Description

BACKGROUND

1. Field

This application relates to an articulated mechanical arm, such as an articulated robotic arm. Articulated arms comprise a series of links which are connected by articulate joints allowing movement of the links with respect to each other. The movement of the links with respect to each other is driven by a drive structure, also know as driver or drive system.

2. Description of Related Art

There is a drive structure using wires as a structure that allows a mechanism configured by a plurality of links to be driven. In the drive structure using the wires, a driver is not directly connected to an end effecter or an articulated joint through which one link is joined to another link, but is located at a part that has no motion or little motion, so the link may be minimized in weight, size, and inertia. Therefore, an advantageous design is possible in terms of driving efficiency and stability of a robot.
In the drive structure using the wires, the wires are typically connected to the driver via a plurality of moving links. In this case, a length of a path of each wire varies according to a motion of a link between the end effecter and the driver and a motion of the articulated joint through which one link is joined to another link, thereby resulting in a coupled motion of the end effecter. That is, the motion of the link or the articulated joint will cause the end effecter to move even if the driver is in a fixed state.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In one general aspect, an apparatus according to the invention includes a link unit; and a drive unit configured to drive the link unit; wherein the link unit includes a first link; a second link rotatably coupled to the first link; a third link rotatably coupled to the second link; a plurality of wires, each of which is fixed at one end thereof to the third link, and is connected at the other end thereof to the drive unit, and through which a driving force is transmitted from the drive unit to the third link; a path forming structure configured to define for each of the wires a path between the drive unit and the third link; and a length holding structure configured to hold substantially constant a length that each of the wires extends between the drive unit and the third link.
In other words, the length holding structure is configured to hold substantially constant for each of the wires the length of a path between the drive unit and the third link. For example, each of the wires is fixed at said one end to a corresponding fixing point on the third link and connected to the drive unit at a connection point. The length of the path between the connection point on the drive unit and the fixing point on the third link is kept substantially constant.
When the drive unit operates the wires, i.e. rotates the third link with respect to the second link, the path length of each of the wires may change. However, the length holding structure ensures that for a given position of the third link with respect to the second link the length of the part of the wire extending between the drive unit is kept substantially constant. In other words, the length holding structure ensures that the path length of each of the wires is independent of rotation of the second link with respect to the first link.
In the context of the invention, the term "wire" may also include a cable or a belt.
The second link may be rotatably coupled to the first link by means of a first rotation shaft and the first link may include a second rotation shaft; and the path forming structure may include a first pulley provided on the second link; a second pulley rotatably coupled to the second rotation shaft; a third pulley provided on the second pulley; and a plurality of fourth pulleys provided on the second pulley.
The first link may include both the first rotation shaft and the second rotation shaft that are spaced apart from each other.
The first pulley may further be rotatably coupled to the first rotation shaft, the third pulley may be rotatably coupled to the second rotation shaft and the plurality of fourth pulleys may be rotatably coupled on the second pulley.
The plurality of wires may be wound around the first pulley, the second pulley, the fourth pulleys, and the third pulley in serial order from the third link to the drive unit.
The plurality of wires may include a first wire and a second wire; and the first wire may be wound around the first pulley in a first direction, wound around the second pulley and the fourth pulleys in a second direction opposite to the first direction, and wound around the third pulley in the first direction.
The second wire may be wound around each of the first pulley, the second pulley, the fourth pulleys, and the third pulley in a direction opposite to the direction in which the first wire is wound around each of the first pulley, the second pulley, the fourth pulleys, and the third pulley.
The length holding structure may include a first interlocking gear provided on the second link; and a second interlocking gear provided on the second pulley to engage with the first interlocking gear. For example, the first gear may be fixed to the second link or integrally formed with the second link. For example, the second gear may be fixed to the second pulley or integrally formed with the second pulley.
The second interlocking gear may be configured to rotate in a direction opposite to the rotation of the second link with respect to the first link.
A sum of a radius of the first pulley and a radius of the second pulley may be equal to a length of a straight line between a center of rotation of the first pulley and a center of rotation of the second pulley.
A sum of a radius of the third pulley and a diameter of each of the fourth pulleys may be equal to a radius of the second pulley.
The fourth pulleys may be a pair of fourth pulleys; and the pair of fourth pulleys may be symmetrically arranged with respect to a straight line joining a center of rotation of the first pulley and a center of rotation of the second pulley.
The plurality of wires may include at least one pair of wires and the apparatus may further include a diverging means configured to diverge the paths of the wires of said pair from each other; and joining means configured to join the paths of the wires of said pair.
The plurality of wires may include a pair of first wires and a pair of second wires; the apparatus may further include a first divergence roller disposed between the third link and the first pulley to diverge the pair of first wires from each other; a second divergence roller disposed between the third link and the first pulley to diverge the pair of second wires from each other; a first coupling roller disposed between the third pulley and the drive unit to couple together the pair of first wires that are diverged from each other; and a second coupling roller disposed between the third pulley and the drive unit to couple together the pair of second wires that are diverged from each other; and the wires of each pair may be wound around the first pulley, the second pulley, the fourth pulleys, and the third pulley in directions opposite to each other.
In another general aspect, an apparatus includes a link unit; and a drive unit configured to drive the link unit; wherein the link unit may include a first link; a second link rotatably coupled to the first link; a third link rotatably coupled to the second link; a first pulley configured to freely rotate about a same axis as the second link; a second pulley configured to interlock with the second link and rotate as the second link rotates; a third pulley configured to freely rotate about a same axis as the second pulley; a plurality of fourth pulleys coupled to the second pulley and configured to freely rotate; and a plurality of wires connected from the third link to the drive unit via, in serial order, the first pulley, the second pulley, the fourth pulleys, and the third pulley.
The plurality of wires may include a first wire and a second wire; the first wire may be wound around the first pulley in a first direction, wound around the second pulley and a first one of the fourth pulleys in a second direction opposite to the first direction, and wound around the third pulley in the first direction; and the second wire may be wound around each of the first pulley, the second pulley, a second one of the fourth pulleys, and the third pulley in a direction opposite to the direction in which the first wire is wound around each of the first pulley, the second pulley, the first one of the fourth pulleys, and the third pulley.
The apparatus may further include a first interlocking gear arranged in the second link; and a second interlocking gear arranged in the second pulley to engage with the first interlocking gear.
The second pulley may be configured to rotate in the second direction as the second link rotates in the first direction to hold constant respective lengths of the first wire and the second wire between the third link and the drive unit; and the second pulley may be further configured to rotate in the first direction as the second link rotates in the second to hold constant the respective lengths of the first wire and the second wire between the third link and the drive unit.
The plurality of wires may include a pair of first wires and a pair of second wires; and the apparatus may further include a first divergence roller disposed between the third link and the first pulley to diverge the pair of first wires from each other; a second divergence roller disposed between the third link and the first pulley to diverge the pair of second wires from each other; a first coupling roller disposed between the third pulley and the drive unit to couple the pair of first wires that are diverged from each other; and a second coupling roller disposed between the third pulley and the drive unit to couple the pair of second wires that are diverged from each other.
In another general aspect, an apparatus includes a base link; a middle link rotatably coupled to the base link and configured to rotate relative to the base link without changing an axis of rotation of the middle link; an end effecter rotatably coupled to the middle link; and at least one wire traversing a path along the base link and the middle link from a reference point and fixed to the end effecter; wherein a length of the at least one wire from the reference point to the end effecter is held constant even when the middle link rotates.
The apparatus may further include a drive unit; and the reference point may be a portion of the drive unit.
The at least one wire may include a first wire traversing a first path between the reference point and the end effecter; and a second wire traversing a second path different from the first path between the reference point and the end effecter.
The at least one wire may include a pair of wires that are diverged from each other in at least a partial section of the connection apparatus between the reference point and the end effecter.
In another general aspect, an apparatus includes a base link; a middle link rotatably coupled to the base link and configured to rotate relative to the base link about an axis of rotation that is fixed relative to the base link; an end effecter rotatably coupled to the middle link; at least one wire fixed to the end effecter and traversing a path from the end effecter to at least one reference point along the middle link and the base link; and a path forming structure configured to hold constant a length of the at least one wire from the reference point to the end effecter as the middle link rotates without diverging the at least one wire from the middle link and the base link.
The path forming structure may prevent the end effecter from moving relative to the middle link as the middle link rotates when a driving force is not applied to the end effecter.
The reference point may include a first reference point and a second reference point different from the first reference point; and the at least one wire may include a first wire traversing a first path from the end effecter to the first reference point; and a second wire traversing a second path from the end effecter to the second reference point.
The at least one wire may include a first wire traversing a first path from the end effecter to the reference point; and a second wire traversing a second path different from the first path from the end effecter to the reference point.
The first wire and the second wire may traverse a same path in a portion of the first path and a portion of the second path; and the first wire and the second wire may traverse different paths in another portion of the first path and another portion of the second path.
Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a link unit and a drive unit.
FIGS. 2A and 2B illustrate examples of a state in which the link unit is driven and operated.
FIG. 3 is a diagram for explaining a rotation ratio between a first interlocking gear and a second interlocking gear to hold constant lengths of a first wire and a second wire constant.
FIGS. 4A and 4B illustrate another example of a link unit and a drive unit, and illustrate an example of a structure that forms paths of a pair of first wires and a pair of second wires.
FIGS. 5A and 5B are diagrams for explaining a principle by which a difference in tensions applied to the first wires and the second wires is offset.

DETAILED DESCRIPTION

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience.
In this application, for convenience of description, a first direction A refers to a clockwise direction, and a second direction B refers to a counterclockwise direction.
FIG. 1 illustrates an example of a link unit and a drive unit. FIGS. 2A and 2B illustrate examples of a state in which the link unit is driven and operated.
As shown in FIGS. 1 to 2B, an apparatus 10 includes a link unit 100 and a drive unit 200 to drive the link unit 100.
The link unit 100 includes a plurality of links 110, 120, and 130 arranged in a line, a plurality of wires or cables 140 and 150 through which a driving force of the drive unit 200 is transmitted to the link 130 constituting an end effecter 130, a path forming structure 160 to form paths of the wires 140 and 150 between the drive unit 200 and the end effecter 130, and a length holding structure 170 to keep the length that the wires 140 and 150 extend between the drive unit 200 and the end effecter 130 constant, or substantially constant.
The plurality of links 110, 120, and 130 include a base link 110, a middle link 120 rotatably coupled to the base link 110, and an end effecter 130 rotatably coupled to the middle link 120.
The base link 110 includes a first rotation shaft 112 rotatably coupled with the middle link 120 and a first pulley 162 that will be described later, and a second rotation shaft 114 rotatably coupled to a second pulley 164 and a third pulley 166 that will be described later. The first and second rotation shafts 112 and 114 protrude from one side of the base link 110 and are spaced apart from each other on the one side of the base link 110.
The middle link 120 includes a third rotation shaft 122 rotatably coupled with the end effecter 130.
The end effecter 130 is provided with a first wire fixing portion 132 and a second wire fixing portion 134 to which respective ends of the wires 140 and 150 are fixed.
The end effecter 130 is not limited to being a link located at an end or a tip of the link unit 100 only, but may be a link between the links or another middle link. Accordingly, for convenience of description below, the base link 110, the middle link 120, and the end effecter 130 will be referred to as a first link 110, a second link 120, and a third link 130 in order of increasing distance from the drive unit 200.
The wires 140 and 150 include a first wire 140 and a second wire 150 to rotate the third link 130 with respect to second link 120.
One end 142 of the first wire 140 is fixed to the first wire fixing portion 132 of the third link 130, and the other end 144 of the first wire 140 is connected to a first connecting portion 212 of the drive unit 200, which may serve as a reference point for measuring the path length of the wire 140 from the drive unit to the first wire fixing portion 132.
Similarly, one end 152 of the second wire 150 is fixed to the second wire fixing portion 134 of the third link 130, and the other end 154 of the second wire 150 is connected to a second connecting portion 214 of the drive unit 200, which may serve as a reference point for measuring the path length of the wire 150 from the drive unit to the second wire fixing portion 134.The first connecting portion 212 and the second connecting portion 214 of the drive unit 200 may each comprise a feedthrough. The wires 140, 150 pass through the feedthroughs 212, 214 to the drive unit 200. The drive unit is arranged to apply a difference in tension to the first and second wires 140, 150 to move the third link 130 with respect to the second link 120. In other words, the drive unit is arranged to pull or loosen wires 140, 150 to rotate the third link 130 with respect to second link 120.
When a difference in tension is applied to the first and second wires 140, 150, the third link rotates in the first direction A or the second direction B opposite to the first direction A.
The path forming structure 160 includes the first pulley 162 rotatably coupled to the first rotation shaft 112, the second pulley 164 rotatably coupled to the second rotation shaft 114, the third pulley 166 rotatably coupled to the second rotation shaft 114 and spaced apart from the second pulley 164 in an axial direction of the second rotation shaft 114, and a pair of fourth pulleys 168a and 168b rotatably coupled to the second pulley 164.
The first pulley 162 is coupled to the first rotation shaft 112 so as to freely rotate about the first rotation shaft 112. The first and second wires 140 and 150 are wound around the first pulley 162 in opposite directions to each other. In the examples of FIGS. 1, 2A and 2B, the first wire 140 is wound around the first pulley 162 in the first direction A when viewed from the first wire fixing portion 132, and the second wire 150 is wound around the first pulley 162 in the second direction B when viewed from the second wire fixing portion 134.
The second pulley 164 interlocks with the second link 120 and rotates by the action of the length holding structure 170 that will be described later, and includes a pair of fourth rotation shafts 164a and 164b rotatably coupled with the pair of fourth pulleys 168a and 168b. The first and second wires 140 and 150 are wound around the second pulley 164 in opposite directions to each other. In the examples of FIGS. 1, 2A and 2B, the first wire 140 is wound around the second pulley 164 in the second direction B when viewed from the first wire fixing portion 132, and the second wire 150 is wound around the second pulley 164 in the first direction A when viewed from the second wire fixing portion 134.
The first and second pulleys 162 and 164 may be arranged such that a sum of a radius R1 of the first pulley 162 and a radius R2 of the second pulley 164 is equal, or substantially equal, to a length of a straight line L1 between a center of rotation C1 of the first pulley 162 and a center of rotation C2 of the second pulley 164.
The third pulley 166 is coupled to the second rotation shaft 114 so as to freely rotate about the second rotation shaft 114. The first and second wires 140 and 150 are wound around the third pulley 166 in opposite directions to each other. In the examples of FIGS. 1, 2A and 2B, the first wire 140 is wound around the third pulley 166 in the first direction A when viewed from the first wire fixing portion 132, and the second wire 150 is wound around the third pulley 166 in the second direction B when viewed from the second wire fixing portion 134.
The pair of fourth pulleys 168a and 168b are coupled to the pair of fourth rotation shaft 164a and 164b, respectively, so as to freely rotate about the pair of fourth rotation shaft 164a and 164b, respectively. The first and second wires 140 and 150 are wound around the fourth pulleys 168a and 168b, respectively, in opposite directions to each other. In the examples of FIGS. 1, 2A and 2B, the first wire 140 is wound around the pulley 168b of the pair of fourth pulleys 168a and 168b in the second direction B when viewed from the first wire fixing portion 132, and the second wire 150 is wound around the fourth pulley 168a in the first direction A when viewed from the second wire fixing portion 134.
The third pulley 166 and the pair of fourth pulleys 168a and 168b may be arranged such that a sum of a radius R3 of the third pulley 166 and a diameter 2 x R4 of each of the pair of fourth pulleys 168a and 168b is equal, or substantially equal, to a radius R2 of the second pulley 164.
In addition, the pair of fourth pulleys 168a and 168b may be symmetrically, or substantially symmetrically, arranged with respect to the straight line L1 joining the center of rotation C1 of the first pulley 162 and the center of rotation C2 of the second pulley 164.
To summarize the paths of the first and second wires 140 and 150 defined by the above-mentioned path forming structure 160, the first wire 140 is fixed to the first wire fixing portion 132, moves along the second link 120, is wound around the first pulley 162 in the first direction A, is wound around the second and fourth pulleys 164 and 168b in the second direction B, is wound around the third pulley 166 in the first direction A, and is then fixed to the first connecting portion 212. The second wire 150 is fixed to the second wire fixing portion 134, moves along the second link 120, is wound around the first pulley 162 in the second direction B, is wound around the second and fourth pulleys 164 and 168a in the first direction A, is wound around the third pulley 166 in the second direction B, and is then connected to the second connecting portion 214.The length holding structure 170 includes a first interlocking gear 172 arranged in the second link 120 and a second interlocking gear 174 arranged in the second pulley 164 to engage with the first interlocking gear 172. Preferably, the first gear 172 is fixed relative to second link 120 and second gear 174 is fixed relative to second pulley 164 such that it can rotate together with second pulley 164 with respect to first link 110. The first interlocking gear 172 may be formed integrally with the second link 120, and the second interlocking gear 174 may be formed integrally with the second pulley 164.
The second interlocking gear 174 allows the second pulley 164 to rotate in a direction opposite to the rotation direction of the second link 120 during rotation of the second link 120 relative to the first link 110, with the consequence that the length of the first wire 140 between the first wire fixing portion 132 and the first connecting portion 212 and the length of the second wire 150 between the second wire fixing portion 134 and the second connecting portion 214 are held constant.
As shown in FIG. 2A, when the second interlocking gear 174 engaging with the first interlocking gear 172 and the second pulley 164 rotate in the second direction B as the second link 120 and the first interlocking gear 172 rotate in the first direction A, the length of the first wire 140 between the first wire fixing portion 132 and the first connecting portion 212 and the length of the second wire 150 between the second wire fixing portion 134 and the second connecting portion 214 are held constant.
For the first wire 140, a point K is defined as the point at which the first wire 140 is decoupled from the second link 120 and begins to be wound around the second pulley 164 (figure 2A). By rotation of the second link 120 and the first interlocking gear 172 in the first direction A, the length of the first wire 140 from the first wire fixing portion 132 to the point K is decreased, compared with a state in which the second link 120 and the first link 110 are arranged in a straight line as shown in FIG. 1. In this case, however, the length of the first wire 140 to the first connecting portion 212 from the point K is increased by rotation of the second pulley 164 in the second direction B, thereby offsetting the decreased length of the first wire 140 from the first wire fixing portion 132 to the point K. Consequently, the length of the first wire 140 between the first wire fixing portion 132 and the first connecting portion 212 is always held constant.
For the second wire 150, the point K is defined as the point at which the second wire 140 is decoupled from the second link 120 and begins to be wound around the second pulley 164 (figure 2B). By rotation of the second link 120 and the first interlocking gear 172 in the first direction A the length of the second wire 150 from the second wire fixing portion 134 to the point K is increased, compared with a state in which the second link 120 and the first link 110 are arranged in a straight line as shown in FIG. 1. In this case, however, the length of the second wire 150 to the second connecting portion 214 from the point K is decreased by rotation of the second pulley 164 in the second direction B, thereby offsetting the increased length of the second wire 150 from the second wire fixing portion 134 to the point K. Consequently, the length of the second wire 150 between the second wire fixing portion 134 and the second connecting portion 214 is always held constant.
As shown in FIG. 2B, when the second interlocking gear 174 engaging with the first interlocking gear 172 and the second pulley 164 rotate in the first direction A as the second link 120 and the first interlocking gear 172 rotate in the second direction B, the length of the first wire 140 between the first wire fixing portion 132 and the first connecting portion 212 and the length of the second wire 150 between the second wire fixing portion 134 and the second connecting portion 214 are held constant.
The length of the first wire 140 from the first wire fixing portion 132 to the point K is increased by rotation of the second link 120 and the first interlocking gear 172 in the second direction B, compared with a state in which the second link 120 and the first link 110 are arranged in a straight line as shown in FIG. 1. In this case, however, the length of the first wire 140 to the first connecting portion 212 from the point K is decreased by rotation of the second pulley 164 in the first direction A , thereby offsetting the increased length of the first wire 140 from the first wire fixing portion 132 to the point K. Consequently, the length of the first wire 140 between the first wire fixing portion 132 and the first connecting portion 212 is always held constant.
In addition, the length of the second wire 150 from the second wire fixing portion 134 to the point K is decreased by rotation of the second link 120 and the first interlocking gear 172 in the second direction B, compared with a state in which the second link 120 and the first link 110 are arranged in a straight line as shown in FIG. 1. In this case, however, the length of the second wire 150 to the second connecting portion 214 from the point K is increased by rotation of the second pulley 164 in the first direction A, thereby offsetting the decreased length of the second wire 150 from the second wire fixing portion 134 to the point K at which the second wire 150 is decoupled from the second link 120 and begins to be wound around the second pulley 164. Consequently, the length of the second wire 150 between the second wire fixing portion 134 and the second connecting portion 214 is always held constant.
FIG. 3 is a diagram for explaining a rotation ratio between the first interlocking gear and the second interlocking gear to hold constant the lengths of the wires 140 and 150 constant.
As shown in FIG. 3, assuming that the length of the first wire 140 between the first wire fixing portion 132 and the first connecting portion 212 is held constant when the second link 120 and the first interlocking gear 172 rotate in the first direction A by θa° and the second pulley 164 interlocks with the second link 120 and the first interlocking gear 172 and rotates in the second direction B by θb°, the decreased length La of the first wire 140 from the first wire fixing portion 132 to the point K at which the first wire 140 is decoupled from the second link 120 and begins to be wound around the second pulley 164 is expressed by the following Equation 1. $La = R 1 \times θa$
Meanwhile, the increased length Lb of the first wire 140 to the first connecting portion 212 from the point K is expressed by the following Equation 2. $Lb = (R 2 \times θb) + (R 3 \times θb)$
In addition, since the sum of the radius R3 of the third pulley 166 and the diameter 2xR4 of each of the pair of fourth pulleys 168a and 168b is equal to the radius R2 of the second pulley 164, the following Equation 3 may be established. $R 2 = R 3 + (2 \times R 4)$
The following Equation 4 is obtained by substituting Equation (3) into Equation (2). $Lb = 2 \times θb \times (R 3 + R 4)$
Since the decreased length La of the first wire 140 from the first wire fixing portion 132 to the point K is equal to the increased length Lb of the first wire 140 to the first connecting portion 212 from the point K , the following Equation 5 is satisfied. $R 1 \times θa = 2 \times θb \times (R 3 + R 4)$
The following Equation 6 is obtained by rearranging Equation (5). $θa / θb = 2 \times (R 3 + R 4) / R 1$
Accordingly, the rotation ratio between the first interlocking gear 172 and the second interlocking gear 174 to hold constant the length of the first wire 140 constant is expressed by the following Equation 7. $θa : θb = 2 \times (R 3 + R 4) : R 1$
The rotation ratio between the first interlocking gear 172 and the second interlocking gear 174 to hold constant the length of the second wire 150 is the same as described above, so no detailed description will be provided.
As described above, since the length of the first wire 140 between the first wire fixing portion 132 and the first connecting portion 212 and the length of the second wire 150 between the second wire fixing portion 134 and the connecting portion 214 by interlocking of the first and second interlocking gears 172 and 174 are always held constant during rotation of the second link 120 in the first direction A or the second direction B, the third link 130 is prevented from rotating relative to the second link 120 in an unwanted direction. In other words, the path length from the drive unit 200 to the fixing point 132 is independent of the rotation of second link 120 relative to first link 110, due to the length holding structure 170.
Another example will now be described. No description will be provided of the same parts as example described above.
FIGS. 4A and 4B are diagrams illustrating a link unit and a drive unit according to another example, and illustrating a structure forming paths of a pair of first wires and a pair of second wires.
Although the pair of first wires 140a and 140b and the pair of second wires 150a and 150b are included in the same link unit and are simultaneously operated, the first wires 140a are shown in FIG. 4A and the second wires 140b are shown in FIG. 4B for convenience of description.
As shown in FIGS. 4A and 4B, the wires 140a, 140b, 150a, and 150b include a pair of first wires 140a and 140b and a pair of second wires 150a and 150b. The link unit 100 further includes a first divergence roller 182 disposed between the third link 130 and the first pulley 162 to diverge the pair of first wires 140a and 140b, a second divergence roller 184 spaced apart from the first divergence roller 182 and disposed between the third link 130 and the first pulley 162 to diverge the pair of second wires 150a and 150b, a first coupling roller 192 disposed between the third pulley 166 and the drive unit 200 to couple the pair of first wires 140a and 140b diverged by the first divergence roller 182, and a second coupling roller 194 spaced apart from the first coupling roller 192 and disposed between the third pulley 166 and the drive unit 200 to couple the pair of second wires 150a and 150b diverged by the second divergence roller 184.
As shown in FIG. 4A, the pair of first wires 140a and 140b are fixed to the first wire fixing portion 132, move along the second link 120, and are diverged by the first divergence roller 182. The diverged wires 140a and 140b are wound around each of the first pulley 162, the second pulley 164, the fourth pulleys 168a and 168b, and the third pulley 166 in opposite directions to each other, and are coupled again by the first coupling roller 192. Then, the coupled wires 140a and 140b are fixed together to the first connecting portion 212 of the drive unit 200.
As shown in FIG. 4B, the pair of second wires 150a and 150b are fixed to the second wire fixing portion 134, move along the second link 120, and are diverged by the second divergence roller 184. The diverged wires 150a and 150b are wound around each of the first pulley 162, the second pulley 164, the fourth pulleys 168a and 168b, and the third pulley 166 in opposite directions to each other, and are coupled again by the second coupling roller 194. Then, the coupled wires 150a and 150b are fixed together to the connecting portion 214 of the drive unit 200.
By providing a structure of diverging and coupling the plural wires 140a, 140b, 150a, and 150b as described above, it may be possible to eliminate torque disturbance occurring in the second link 120 due to a difference in tensions applied to the pair of first wires 140a and 140b and the pair of second wires 150a and 150b.
FIGS. 5A and 5B are diagrams for explaining a principle in which a difference in tensions applied to the first wires and the second wires is offset.
As shown in FIGS. 5A and 5B, when a difference ΔT is generated between a tension T applied to the pair of first wires 140a and 140b and a tension T + ΔT applied to the pair of second wires 150a and 150b, a force 2T applied in each of directions P1 and P2 toward a center of rotation C1 of the first pulley 162 by the pair of first wires 140a and 140b and a force 2T + 2ΔT applied in each of directions P1 and P2 toward a center of rotation C1 of the first pulley 162 by the pair of second wires 150a and 150b are applied to each of the fourth pulleys 168a and 168b. Thus, the magnitude of the resultant force F1 applied to the fourth pulley 168a of the fourth pulleys 168a and 168b is 2T + 2T + 2ΔT, and the direction of the resultant force F1 applied thereto is a direction P1 toward the center of rotation C1 of the first pulley 162. In addition, the magnitude of the resultant force F2 applied to fourth pulley 168b of the fourth pulleys 168a and 168b is 2T + 2T + 2ΔT, and the direction of the resultant force F2 applied thereto is a direction P2 toward the center of rotation C1 of the first pulley 162.
Since the fourth pulleys 168a and 168b are symmetrically arranged with respect to the straight line L1 joining the center of rotation C1 of the first pulley 162 and the center of rotation C2 of the second pulley 164 as described above in connection with FIGS. 1 to 2B, an overlapping direction of the resultant force F1 applied to the fourth pulley 168a of the fourth pulleys 168a and 168b and the resultant force F2 applied to the fourth pulley 168b of the fourth pulleys 168a and 168b is parallel with the straight line L1 joining the center of rotation C1 of the first pulley 162 and the center of rotation C2 of the second pulley 164. Therefore, the torque disturbance occurring in the second link 120 due to a difference in tensions applied to the pair of first wires 140a and 140b and the pair of second wires 150a and 150b is offset, and motion of the second link 120 may be more accurately controlled.
Accordingly, unlike the link unit of the example of FIGS. 1 to 2B, the link unit of the example of FIGS. 4A and 4B includes the pair of first wires 140a and 140b and the pair of second wires 150a and 150b diverged in a partial section of the link unit.
In an alternative embodiment, only the second pulley 164 is rotatably coupled to the second shaft 114, whereas first pulley 162 may be fixed to link 120, third pulley 166 may be fixed to the second pulley 164 and/or the fourth pulleys 168a, 168b may be fixed to the second pulley 164. However, preferably also pulleys 164, 166 168a, 168b are rotatable.
While this disclosure includes specific examples, it will be apparent to one of ordinary skill in the art that various changes in form and details may be made in these examples without departing from the scope of the claims and their equivalents. Suitable results may be achieved if components in a described device are combined in a different manner, and/or replaced or supplemented by other components or their equivalents. Therefore, the scope of the disclosure is defined not by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as being included in the disclosure.

Claims

An apparatus comprising:
a link unit; and

a drive unit configured to drive the link unit;
wherein the link unit comprises:
a first link;

a second link rotatably coupled to the first link;

a third link rotatably coupled to the second link;

a plurality of wires, each of which is fixed at one end thereof to the third link, and is connected at the other end thereof to the drive unit, and through which a driving force is transmitted from the drive unit to the third link;

a path forming structure configured to define for each of the wires a path between the drive unit and the third link; and

a length holding structure configured to hold substantially constant a length that each of the wires extends between the drive unit and the third link.
The apparatus of claim 1, wherein the second link is rotatably coupled to the first link by means of a first rotation shaft and the first link comprises a second rotation shaft; and
the path forming structure comprises:
a first pulley provided on the second link;

a second pulley rotatably coupled to the second rotation shaft;

a third pulley provided on the second pulley; and

a plurality of fourth pulleys provided on the second pulley.
The apparatus of claim 2, wherein the first link comprises the first rotation shaft, and the first and second rotation shaft are spaced apart from each other.
The apparatus according to claim 2 or 3, wherein the first pulley is rotatably coupled to the first rotation shaft, the third pulley is rotatably coupled to the second rotation shaft and the plurality of fourth pulleys are rotatably coupled on the second pulley.
The apparatus of claim 2, 3 or 4, wherein the plurality of wires are wound around the first pulley, the second pulley, the fourth pulleys, and the third pulley in serial order from the third link to the drive unit.
The apparatus of claim 5, wherein the plurality of wires comprise a first wire and a second wire; and
the first wire is wound around the first pulley in a first direction, wound around the second pulley and the fourth pulleys in a second direction opposite to the first direction, and wound around the third pulley in the first direction.
The apparatus of claim 6, wherein the second wire is wound around each of the first pulley, the second pulley, the fourth pulleys, and the third pulley in a direction opposite to the direction in which the first wire is wound around each of the first pulley, the second pulley, the fourth pulleys, and the third pulley.
The apparatus of any of the claims 2-7, wherein the length holding structure comprises:
a first interlocking gear provided on the second link; and

a second interlocking gear provided on the second pulley to engage with the first interlocking gear.
The wire connection apparatus of claim 8, wherein the second interlocking gear is configured to rotate in a direction opposite to the rotation of the second link with respect to the first link.
The apparatus of any of the claims 2-9, wherein a sum of a radius of the first pulley and a radius of the second pulley is equal to a length of a straight line between a center of rotation of the first pulley and a center of rotation of the second pulley.
The apparatus of any of the claims 2-10, wherein a sum of a radius of the third pulley and a diameter of each of the fourth pulleys is equal to a radius of the second pulley.
The apparatus of any of the claims 2-11, wherein the fourth pulleys are a pair of fourth pulleys; and
the pair of fourth pulleys are symmetrically arranged with respect to a straight line joining a center of rotation of the first pulley and a center of rotation of the second pulley.
The apparatus of any of the claims 2-12, wherein the plurality of wires comprises at least one pair of wires, the apparatus comprising
diverging means configured to diverge the paths of the wires of said pair from each other; and
joining means configured to join the paths of the wires of said pair.
The apparatus of any of the claims 2-13, wherein the plurality of wires comprise a pair of first wires and a pair of second wires; and
the apparatus further comprises:
a first divergence roller disposed between the third link and the first pulley to diverge the pair of first wires from each other;

a second divergence roller disposed between the third link and the first pulley to diverge the pair of second wires from each other;

a first coupling roller disposed between the third pulley and the drive unit to couple together the pair of first wires that are diverged from each other; and

a second coupling roller disposed between the third pulley and the drive unit to couple together the pair of second wires that are diverged from each other;

wherein the wires of each pair are wound around the first pulley, the second pulley, the fourth pulleys, and the third pulley in directions opposite to each other.